So, I want the game to be mainly focused on solving puzzles, and because of that, I am not planning on adding any enemy soon (at least not the ones that damages the player). For the time being, I'll dedicate my time on implementing the main mechanics of the puzzle-solving part of the game. So, my interest lays on developing:

• Implement the other playable characters and their mechanics

Adding the archer who can shoot at a distance, a monk or someone who can move boulders or heavy stuff and a witch who can alter the magic items in the map.

• A way to be able to switch between characters. 

The game will start with just one character, and as the player moves forward, more characters are unlocked if they are encountered in the game. I want to make it so that at each floor, the party will start at a "safe room" or a room that the party has made their own. I want it so that once the player enters a room with another character, the player can switch between these characters. So, eventually, the player may have the whole party scattered through the level in order to solve the puzzle and move to the next level.

• A way to add difficulty to the game.

Since enemies won't be added (not sure if ever),  I'm looking for another way to add tension or a sense of danger that doesn't necessarily involves defeating enemies. I've come up with two ideas which may or may not be awful:

1. Sanity. If you have played "Don't Starve" you may know what I'm talking about. In this particular case, when sanity is lowered, the player will not loose health, nor dark enemies appear. Instead, I'm thinking there will be two consequences: The first being that the characters the player isn't controlling, will start to wonder around the level, acting on their own accord, activating or deactivating switches and making it more difficult to solve the level.And the second consequence is that, for the character the player is controlling, the light will become dimmer and dimmer until there's complete darkness all around.
2. Captured. In a way, this would involve enemies, but not the fighting part, which is what I am looking to avoid, this would be a mechanic often seen in the Zelda games, where link is captured as soon as he is seen (no fight involved). If one of the members of the party gets captured, that would increase the difficulty of the game. You would need to either rescue the captured one or find another solution.

I still not have decided between 1 or 2, because both seem harder than what I could (probably) achieve. Then I also want to add:

• A way to communicate without using letters.

I've been thinking I want to make a game that doesn't need to be translated, hence, I have been thinking on how to make it easy for people to understand some instructions or communication between characters. I'm thinking I'm going to be using some sort of emoji-like method to communicate ideas. Like for example, if there is a room that has some sort of timer before the door are closed, there would be an npc that would warn you by showing a globe above his head with a clock on it. Or maybe there would be a tablet or old wall with emoji-like inscriptions showing some piece of information. I still need to think this through but I think I like the idea and I'll give it a shot.

So far this what I'll be working on. Please, share your thoughts and let me know if there's any other mechanic or thing I could add to the game that would make it better. Thank you.